I'm in the military and I'm moving to California in a few weeks. I have many hi capacity magazines for the M4 and M9 that were issued to me by the Army and I use them only for work. I don't own either of those weapon systems. What would I have to do to not get in trouble for this.

Your Uncle issued them to you, and expects you to have them.

I'd buy a ticket to the court hearing where a Federal judge explained that to any CA LE agency, but that's an explicit exemption to the goofy law.

Just don't use them in privately owned weapons that have 'features' - see footnote in first post.

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No one will really understand politics until they understand that politicians are not trying to solve our problems. They are trying to solve their own problems - of which getting elected and re-elected are number one and number two. Whatever is number three is far behind.
- Thomas Sowell

I've been saying that for years ...

There is no value at all complaining or analyzing or reading tea leaves to decide what these bills really mean or actually do; any bill with a chance to pass will be bad for gun owners.